10.1.8 Aligning endpoints

After fitting a mathematical outline of splines and lines to a pixel
outline (see section 10.1.1 Finding pixel outlines), Limn aligns the endpoints on
the fitted outline. This involves simply checking each spline to see if
its starting point and ending point (in either axis) are "close
enough" to each other. If they are, then they are made equal to their
average.

This is useful because even a slight offset of the endpoints can be
produce a noticeable result, especially for straight lines and corners.

By default, "close enough" is half a pixel. You can change this with
the `-align-threshold' option.